Abstract:

Shale gas is produced in mud shale formation with abundant organic matter. The transitional facies formation mud shale has large cumulative thickness and high hydrocarbon content. The gas accumulation potential is good in the western Henan, but the mud shale is characterized by thin single formation, multilayer and big transverse phase change. Because of the lack of large amount of gasbearing tests of the blank area, it is difficult to choose good shale gas formation. This paper takes the Upper Palaeozoic in western Henan province as a research object, makes a correlation and clustering analysis of the various parameters and air content of the mud shale, confirms that the main controlling factors of the air content of the shale are organic matter abundance, rock density, permeability, pyrite content and photoelectric absorption cross section index. A regression analysis is carried out with the air content to get a fitting equation, which has been validated to be good for the determination of fitting. Finally, the gasbearing of the transitional facies shale in the western Henan province has been determined by this method and a great number of gas data have been obtained. Comprehensive factor analysis method is proposed in this paper, making the gasbearing as a main factor, supplemented by secondary factors such as the organic matter maturity, porosity, coefficient of brittleness, thickness, burial depth and area. The reservoir benefit coefficient is calculated to choose a gasbearing horizon, and get the regional advantageous factor to predict favorable area. Use the measured and fitted data of the Upper Palaeozoic in the midwestern and western Henan province, favorable factor is calculated to predict the shale gas advantageous area of Zhuxianzhen, Gongyi and Mianchi by using the comprehensive factor analysis method.

Key words: shale gas, Upper Palaeozoic, favorable area, transitional facies, western Henan